1. Field of the Invention
The present invention relates generally to a drainage pipe network, and in particular, to a method, system, apparatus, and article of manufacture for designing a drainage pipe network based on velocity, slope, and pipe covering.
2. Description of the Related Art
When designing a drainage pipe network, engineers must perform a significant amount of work to calculate pipes manually. Engineers need to calculate pipe size, slope, invert and obvert elevation, and also need to check velocity and the pipe covering to determine if constraints can be met. Such a process requires substantial manual efforts and calculations and often times still results in a poor solution. Accordingly, what is needed is an automated process for calculating the proper drainage pipe size and slope. To better understand these problems, a description of prior art drainage pipe design may be useful.
The design procedure for designing a drainage pipe network is stated in section 7.4 of the Hydraulic Engineering Circular No. 22 (HEC-22) published by the Federal Highway Administration. FIG. 1 illustrates a simplified flow for the manual calculation of a pipe design based on the HEC-22 of the prior art.
At step 102, a pipe slope is assumed (e.g., based on user input or generated by a rule).
At step 104, the pipe size is calculated by manning's equation/formula with a known design flow and manning's number (a full gravity flow may be assumed). Manning's formula is an empirical formula that estimates the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid (e.g., an open channel flow). All flow is such open channels are driven by gravity. The Manning number (also known as the Manning coefficient) is an empirically derived coefficient that is dependent on many factors including surface roughness and sinuosity.
At step 106, according to a calculated result (of the pipe size), an approximate pie size may be selected from a pipe content catalog.
At step 108, the real velocity in the pipe is calculated by Manning's equation.
At step 110, a check is conducted to determine whether the velocity can meet the velocity rule (e.g., if the real velocity is smaller than a maximum [e.g., from a rule] and larger than a minimum velocity [e.g., 3 feet/sec]). If the velocity meets the velocity rule, the pipe design is finished and a solution (that includes the pipe size and slope) is obtained at 112. However, if the velocity rule is not met, the process resumes at step 102 using a new assumed pipe slope (i.e., the slope is adjusted/recalculated and the process starts over).
In the above prior art workflow, there are various problems. The first issue arises with the assumption of the pipe slope at step 102. As the pipe slope increases, pipe size will be decreased and pipe covering will be increased. Accordingly, both too large of a pipe size and too much pipe covering will enlarge the pipe network cost. Accordingly, it is difficult to determine a proper slope.
The second problem arises with respect to the significant amount of work needed by engineers to perform the manual calculation of the pipes. Engineers need to calculate pipe size, slope, invert and obvert elevation, and also need to check the velocity and pipe covering to determine if constraints are met.
A third problem arises in that there is more than one available solution. For each pipe slope, there is a corresponding pipe size. If there are a lot of solutions that all comply with the hydraulic calculations and rules, how does one determine the optimal/best solution? Often times, engineers select one solution manually, depending on experience and special design conditions.